Fence post driver



July 7, 1964 sMlTH 3,139,944

FENCE POST DRIVER Filed Sept. 3, 1963 2 Sheets-Sheet l 10 I 4 I ,l e 10 Fl 9- 3 L i as INVENTOR.

76 1 JOHN D. sM/rH yew 1495M ATTORNEY July 7, 1964 J. D. SMITH FENCE POST DRIVER Filed Sept. 3, 1963 2 Sheets-Sheet 2 P E: m

INVENTOR. JOHN D. SHIT 4%? ATTORNEYS United States Patent 3,139,944 FENCE POST DRIVER John D. Smith, 3033 N. Hayden Road, Scottsdale, Ariz., assignor of one-half to Martensen Enterprises Inc. Filed Sept. 3, 1963, Ser. No. 306,025 13 Claims. (Cl. 173-119) The present invention pertains to post drivers; and more particularly, to fence post drivers that are readily portable and may be utilized in the field without the necessity of cumbersome auxiliary equipment.

Fence posts commonly utilized today are constructed of T-section iron and include a spade tip to prevent rotation of the post once it has been driven into the ground. Several post drivers have been proposed utilizing standard well-known techniques that have been used for years in the construction industry. More specifically, pile drivers utilized to embed pilings for large and heavy structures commonly use steam driven weight-lifting devices that drop the weight through a specified distance on the end of the piling. Weight-dropping techniques have been scaled proportionately to drive fence posts and have supplanted steam techniques with a variety of various types of energy lifts to lift a weight and drop it upon the end of the fence post. Prior art fence post drivers have universally been cumbersome and exceedingly awkward thereby limiting the portability and requiring, in most instances, a large truck or tractor to carry the equipment. Similarly, prior art devices require careful operation to insure that the fence post being driven remains vertical after the driving operation has started.

It is therefore an object of the present invention to provide a fence post driver that is light weight and portable and may be carried on the back of a small vehicle such as, for example, a Jeep.

It is another object of the present invention to provide a fence post driver that may readily operate from the power take-off of a small vehicle.

It is still another object of the present invention to provide a fence post driver that delivers a measured stroke to the fence post while guiding the post to assure that it remains vertical.

It is a further object of the present invention to provide a fence post driver that constantly pushes the fence post downwardly to prevent the post from jumping or skewing while the post is intermittently being driven by impact into the ground.

Further objects and advantages of the present invention will become apparent as the description thereof proceeds.

Briefly, in accordance with one embodiment of the present invention, a pair of frames are mounted for relative movement therebetween and are fixed to opposite ends of a piston and cylinder arrangement. Oneof the frames may be secured to a vehicle and act as a fixed frame; whereas, the second frame, slidable in relation to the first, acts as a movable frame for carrying the driving equipment. A weight, eccentrically mounted on the end of a rotatable shaft, is carried by the movable frame and includes a second shaft extending therefrom that is journaled in a journal block slidably mounted on a rocker arm. As the weight rotates, the rocker arm is forced downwardly through the expediency of a coil spring positioned between the slidable journal and a striker mounted on the pivoted end of the rocker arm. As the rocker arm descends, the striker strikes an anvil that is provided with an opening on the bottom thereof for admission of a top of a fence post.

3,139,944 Patented July 7,, 19.64

The present invention may more readily be described by reference to the accompanying drawings in which:

FIG. 1 is a front elevational view of a fence post driver constructed in accordance with the teachings of the present invention.

FIG. 2 is a right side view of the device shown in FIG. 1.

FIG. 3 is a simplified isometric view of a fence post driver constructed in accordance with the teachings of the present invention mounted on the back of a Jeep.

Referring to FIG. 1, a guiding frame 10 is shown in vertical position and secured to a pivotal mounting bar 11. The bar may be journaled in any convenient manner in journal or pillow blocks 12 and 13 which may be secured to the rear of a vehicle. Thus, the guiding frame is secured to the vehicle and acts as a reference plane upon which the driving mechanism moves. A movable frame 15 is shown slidably attached to the guiding frame, and which includes a pair of pillow blocks 16 and 17 on the top thereof. The pillow blocks journal a rotatable shaft 20 which is connected at one end thereof to a weight 22. The weight 22 (shown more clearly in FIG. 2) is eccentrically mounted on the shaft 20 and is used to add mass to the system as well as to counterbalance the weight of other parts. The opposite end of the rotatable shaft includes a sheave or V-belt pulley 25 secured thereto to impart rotation from the pulley to the shaft. A piston and cylinder arrangement '28 is secured at one end 29 thereof to the guiding frame; the opposite end 30 is connected to the movable frame. The cylinder may conveniently be a pneumatic cylinder or a hydraulic cylinder operable through a hydraulic supply or, in the case of a pneumatic cylinder, may be operated by compressed gas stored 'in a conventional gas cylinder. The piston shaft 32 of the piston and cylinder arrangement may be caused to extend upwardly or retract downwardly in accordance with the pressure admitted to the cylinder 33.

A power take-off 40, of a variety common to many vehicles, may be utilized to drive the fence post driver of the present invention. The power take-off provides rotational power which may be coupled through universal joints 41 and 42 to a driveshaft 45 journaled .at 46 and 47 to the guiding frame 10. The driveshaft 45 mayconveniently be of square cross section to permit ready coupling of the torque delivered thereby to a pulley 48 rotatably supported by a supporting frame 49. Thus, the rotation of the driveshaft is imparted to the pulley through the expediency of the square cross section of the driveshaft. The pulley supporting frame 49 is secured to the movable frame 15 and provides a means for deriving power from the driveshaft to the post driving mechanism. Although the pulley rotates with the driveshaft, the pulley, and the pulley supporting frame, are free to move longitudinally of the driveshaft and thereby permit the longitudinal movement of the movable frame and the equipment mounted thereon.

The pulley support frame '49 also includes a pair of pulleys 51 (only one is shown in the view of FIG. 1) each mounted at right angles to the pulley 48 and each journaled for free rotation. A belt 55, commonly known as a double V-belt, is placed on the pulley 48 and is driven thereby and transmits rotation from pulley 48 around the pair of pulleys 51-to the pulley 25 secured .to the end of the rotatable shaft 20.

A second-shaft 60 is secured to the rotatable weight 22 and extends therefrom into a journal block 61. The journal block 61 can most readily be seen by reference to FIG. 2. The journal block is arranged to be slidable on a rocker arm 62. The rocker arm 62 is pivoted about a horizontal pin 63 and is provided with a pair of compression springs 66 and 67 slidably and concentrically mounted thereon. The compression springs are shown in their approximate balanced position in FIGS. 1 and 2. The rocker arm 62, pivoted at pivot point 63 is secured to a striker 70. The striker, in turn, is slidably supported on a pair of guiding rods 71 and 72 which are attached to the movable frame. Thus, the striker is free to move vertically and, at the bottom of its travel, to engage an anvil 75 which is slidably mounted in an annular ring 76. The opposite end 77 of the anvil 75 is slightly increased in diameter and is hollowed to permit the admission of the top of a fence post. The anvil is shown in FIG. 1 in a position that it would assume when no fence post is presently being driven by the system of the present invention. When a fence post is placed within the hollowed end 77 of the anvil, the anvil will extend upwardly from the ring 76 so that the striker 70 will drive the anvil, and the fence post, downwardly when the striker reaches its bottom position.

Referring to FIG. 2, the fence post driver of the present invention is shown having a diagonally extending supporting member 80 which acts as a strengthening brace to the vertically aligned guiding frame 10. The mounting bar 11 is shown journaled in pillow blocks 12 and 13, and the pillow blocks ar secured (as schematically indicated in FIG. 2) to a vehicle through braces 81 and 82. The inlets and outlets for pneumatic pressure are schematically shown in FIG. 2 at 83 and 84, and the eccentrically mounted weight 22 may readily be seen in its normal or rest position. The coil springs 66 and 67 extending from the striker 70 to the slidable journal block 61 and extending from the slidable journal block to the top of the rocker arm 62, provides several unique advantages which will become apparent as the description of the operation of the present invention is given. The anvil 75, and its enlarged bottom section 77 for admission of the top of a fence post, is shown in its lower most position in the annular ring 76 similar to that indicated in FIG. 1.

It may be seen by reference to FIG. 2 that the guiding frame may be pivoted about the shaft 11 and thus adjusted so that the angle that the fence post is to be driven (usually vertical) may be precisely adjusted. The movable frame may slidably be secured to the guiding frame through the expediency of a pair of clamps 90 and 91 for top and bottom horizontally extending movable frame supporting members 92 and 93 respectively. The view given in FIG. 2 only shows one of each pair of clamps, it being obvious that a similar pair are provided for the supporting arms hidden in FIG. 2. The clamps 90 and 91 are loosely fitted to the guiding frame 10 and the degree of looseness may be controlled by providing shims 95 between the supporting arms and the clamps.

The manner of mounting the fence p'ost driver of the present invention on a small vehicle, such as a Jeep, is shown in part in FIG. 3. It may be seen by reference to FIG. 3 that the scale of the system of the present invention and its compactness permit utilization of the fence post driver on a highly portable vehicle so that the apparatus may be utilized in places heretofore inaccessible to automatic fence post driving equipment. The fence post driver is shown in a vertical position for driving a post; the dotted position shows the driver tilted forward for transport on the vehicle.

The operation of the present invention may be described as follows. The equipment, mounted on the back of a suitable vehicle such as a Jeep, is readily transported to the site of the work. During the transport of the equipment, the piston 32 may be retracted within the cylinder 33 to lower the movable frame 15 to a resting position; similarly, the guiding frame 10 may be locked in a forward tilted position to prevent its rotation about the shaft 11 while it is being transported to the work site (e.g.: see dotted position in FIG. 3). When a fence post is to be driven into the ground, the piston 32 is forced, by pneumatic pressure, to its extended position thus raising the movable frame 15, the pulley supporting frame 49, the striker slide arms 71 and 72, the eccentric weight 22, and the rotatable shaft 20 secured to the weight. The anvil may then be raised to permit a fence post to be placed in a proper position prior to driving it into the ground. The guiding frame may then be unlocked from its transporting position and pivoted about the shaft 11 until it attains a suitably vertical position to insure that the fence post will be driven into the ground.

The hollow end 77 of the anvil may then be positioned above the top of the fence post and the movable frame may be lowered by withdrawing the piston within the cylinder. As the movable frame, and all assemblies secured thereto, are lowered, the hollow portion of the anvil will engage the top of the fence post thus forcing the anvil to project upwardly through the annular ring 76 until the ring engages the shoulder 98 on the enlarged lower portion of the anvil. At this time, the force of the pneumatic pressure exerted on the piston within the cylinder will be transmitted through the movable frame to the anvil supporting ring, to the enlarged anvil end, and subsequently to the top of the fence post to force it downwardly thus holding it securely in position.

The power take-off equipment from the vehicle, or other suitable source of power, may then be engaged to rotate the driveshaft 45. As the driveshaft rotates, the pulley 48 is rotated and the rotation thereof is transmitted through the double V-belt 55 to the pulley 25. The weight 22, eccentrically mounted on the opposite end of the rotatable shaft 20, is thus rotated and the second shaft 60 extending from the weight is thereby revolved about the axis of the first rotatable shaft 20. As the second shaft revolves, it also rotates within the journal block 61 and forces the latter first upwardly and then downwardly of the rocker arm 62. The rocker arm pivots about pivot point 63 while the slidably mounted journal block forces the striker 70 downwardly. The striker guiding rods 71 and 72 guide the striker in its motion downward until it strikes the anvil 75 imparting a severe blow thereto which is transmitted through the anvil to the top of the fence post. The blow imparted by the striker, which causes severe mechanical shock, drives the fence post into the ground and would normally cause a reaction force that would literally lift the bottom end of a small vehicle such as a Jeep off of the ground. This violent reaction is prevented in the fence post driver of the present invention by the inclusion of the coil spring 67 between the slidably mounted journal block and the striker. Thus, the downward force imparted by the great mass of the eccentrically mounted weight and the balancing mass of the striker provides a tremendous impact to the anvil and to the fence post but the reaction therefrom is substantially absorbed in the stiff coil spring positioned between the journal block and the striker. Considerable additional damping may be achieved by the placement of the second coil spring 66, as shown in FIGS. 1 and 2, between the slidable journal block and the top of the rocker arm. The two springs, acting in unison, act as a dampening agent to prevent the transmission of the violent reaction, caused by the impact of the striker with the anvil, to the guiding frame of the fence post driver and subsequently to the vehicle upon which the driver is mounted. When the fence post has been driven by a stroke of the driver, the piston, which has a continuous pneumatic force acting upon it within the cylinder, forces the movable frame to decent in unison with the decent of the fence post into the ground to maintain the hollow portion of the anvil in intimate contact with the top of the fence post. In this manner, the direction that the fence post is being driven is controlled at all times even though the tremendous impact transmitted to the fence post could otherwise cause the post to skew and decend into the ground at other than vertical.

Thus, the fence post driver of the present invention maintains constant pressure and assures intimate contact with the fence post at all times while periodically delivering tremendous impact to the top of the fence post to force it into the ground. To prevent the reaction from the impact from damaging either the fence post driver or the vehicle upon which it is mounted, a unique double coil spring system is utilized that, while not decreasing the efliciency of the driving force, nevertheless absorbs a substantial portion of the reaction force from the impact.

The provision of a sliding power take-off by utilizing a slidably mounted pulley that derives rotation from a driveshaft while permitting longitudinal movement along the shaft, and mounting the pulley on a movable frame containing the above enumerated combination of elements provides a unique and unexpectedly efiicient fence post driver that can be made sufficiently light to be substantially portable without detracting from the driving power which, utilizing prior art fence post drivers, would require much heavier and much bulkier equipment than the apparatus of the present invention.

It will be obvious to those skilled in the art that many modifications of the present invention may be made without departing from the scope of the appended claims, For example, the eccentrically mounted weight may be replaced by a simple force transmitting arm, and a counterbalance may be attached to the opposite end of the rotatable shaft. The specific shape of the eccentrically mounted weight may vary radically, as may the particular shape of the frame, the anvil, the striker, and various other parts of the present invention.

I claim:

1. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; post engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted onsaid movable frame; a weight eccentrically secured to said shaft for rotation therewith; a striker slidably attached to said movableframe and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block secured to said rocker arm; and a second shaft journaled in said journal block and secured to said weight to force said striker against said post engaging means when said weight is rotated.

2. A fence post drive comprising: a guiding frame; a movable frame mounts on said guiding frame and arranged to permit relative motion between said frames; post engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; force transmitting means secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block secured to said rocker arm; and a second shaft journaled in said journal block and secured to said force transmitting means to force said striker against said post engaging means when said force transmitting means is rotated.

3. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; post engaging means slidably secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a weight eccentrically secured to said shaft for rotation therewith; a striker slidably attached to said :movable frame and adapted .to- .strikesaid post engaging means; a rockerarm pivotally attached to said striker; a journal block secured to said rocker arm; a second shaft journaled in said journal block-and secured to said weight to force said striker against said post engaging means when said weight is rotated; a driveshaft journaled to 'said 6 guiding frame; a pulley mounted on said driveshaft for rotation therewith and for free movement longitudinal of said shaft; pulley supporting means connected to said movable frame for rotatably supporting said pulley; and belt means for transmitting the rotation of said pulley to said rotatable shaft.

4. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; post engaging means slidably secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a force transmitting means secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; .a journal block secured to said rocker arm; a second shaft journaled in said journal block and secured to said force transmitting means to force said striker against said post engaging means when said rotatable shaft is rotated; a driveshaft journaled to said guiding frame; a pulley mounted on said driveshaft for rotation therewith and for free movement longitudinal of said shaft; pulley supporting means connected to said movable frame for rotatably supporting said pulley; and belt means for transmitting the rotation of said pulley to said rotatable shaft.

5. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; means for applying force to said movable frame to constantly urge it to move relative to said supporting frame while a fence post is being driven; post engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a weight eccentrically secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block secured to said rocker arm; and a second shaft journaled in said journal block and secured to said weight to force said striker against said post engaging means when said weight is rotated.

6. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; means for applying force to said movable frame to constantly urge it to move relative to said supporting frame while a fence post is being driven; post engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a force transmitting means secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block secured to said rocker arm; and a second shaft journaled in said journal block and secured to said force transmitting means to force said striker against said post engaging means when said weight is rotated.

7. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; piston and cylinder means secured between said guiding and movable frames for applying constant downward force to said movable frame while a fence post is being driven; post engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a weight eccentrically secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block secured to said rocker arm; and a second shaft journaled in said journal block and secured to said weight to force said striker against said post engaging means when said weight is rotated.

8. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; piston and cylinder means secured between said guiding and movable frames for applying constant downward force to said movable frame while a fence post is being driven; post engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a weight eccentrically secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block secured to said rocker arm; a second shaft journaled in said journal block and secured to said weight to force said striker against said post engaging means when said weight is rotated; a driveshaft journaled to said guiding frame; a pulley mounted on said driveshaft for rotation therewith and for free movement longitudinal of said shaft; pulley supporting means connected to said movable frame for rotatably supporting said pulley; and belt means for transmitting the rotation of said pulley to said rotatable shaft.

9. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; piston and cylinder means secured between said guiding and movable frames for applying constant downward force to said movable frame while a fence post is being driven; post engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a weight eccentrically secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block slidably mounted on said rocker arm; spring means mounted on said rocker arm between said journal block and said striker; and a second shaft journaled in said journal block and secured to said weight to compress said spring means and thus force said striker against said post engaging means when said weight is rotated.

10: A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; piston and cylinder means secured between said guiding and movable frames for applying constant downward force to said movable frame While a fence post is being driven; ost engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a force transmitting means secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block slidably mounted on said rocker arm; spring means mounted on said rocker arm between said journal block and said striker; and a second shaft journaled in said journal block and secured to said force transmitting means to compress said spring means and thus force said striker against said post engaging means when said rotatable shaft is rotated.

11, A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; pneumatic piston and cylinder means secured between said guiding and movable frames for applying constant downward force to said movable frame; post engaging means secured to said movable frame for engaging the top of a fence post to be driven into the ground; a rotatable shaft mounted on said movable frame; a weight eccentrically secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block slidably mounted on said rocker arm; a compression spring mounted on said rocker arm between said journal block and said striker; a second shaft journaled in said journal block and secured to said weight to compress said spring means and thus force said striker against said post engaging means when said Weight is rotated; a driveshaft journaled to said guiding frame; a pulley mounted on said driveshaft for rotation therewith and for free movement longitudinal of said shaft; pulley supporting means connected to said movable frame for rotatably supporting said pulley; and belt means for transmitting the rotation of said pulley to said rotatable shaft.

12. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; pneumatic piston and cylinder means secured between said guiding and movable frames for applying constant downward force to said movable frame; post engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a force transmitting means secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said strike; a journal block slidably mounted on said rocker arm; a compression spring mounted on said rocker arm between said journal block and said striker; a second shaft journaled in said journal block and secured to said force transmitting means to compress said spring means and thus force said striker against said post engaging means when said rotatable shaft is rotated; a driveshaft journaled to said guiding frame; a pulley mounted on said driveshaft for rotation therewith and for free movement longitudinal of said shaft; pulley supporting means connected to said movable frame for rotatably supporting said pulley; and belt means for transmitting the rotation of said pulley to said rotatable shaft.

13. A fence post driver comprising: a guiding frame; a movable frame mounted on said guiding frame and arranged to permit relative motion between said frames; pneumatic piston and cylinder means secured between said guiding and movable frames for applying constant downward force to said movable frame while a fence post is being driven; post engaging means secured to said movable frame for engaging the top of a post to be driven into the ground; a rotatable shaft mounted on said movable frame; a force transmitting means secured to said shaft for rotation therewith; a striker slidably attached to said movable frame and adapted to strike said post engaging means; a rocker arm pivotally attached to said striker; a journal block slidably mounted on said rocker arm; a first helical compression spring mounted on said rocker arm between said journal block and said striker; a second helical compression spring mounted on said rocker arm between said journal block and the end of said rocker arm remote from said striker; a second shaft journaled in said journal block and secured to said force transmitting means to compress said spring means and thus force said striker against said post engaging means when said rotatable shaft is rotated; a driveshaft journaled to said guiding frame; a pulley mounted on said driveshaft for rotation therewith and for free movement longitudinal of said shaft; pulley supporting means connected to said movable frame for rotatably supporting said pulley; and belt means for transmitting the rotation of said pulley to said rotatable shaft.

References Cited in the file of this patent UNITED STATES PATENTS 716,019 Feldhus Dec. 16, 1902 880,140 Hastings Feb. 25, 1908 6 Kreis Dec. 26, 1911 5 Smith Feb. 9, 1915 ,8 5 Gunning Apr. 21, 1953 01 Moore Nov. 1, 1960 

2. A FENCE POST DRIVER COMPRISING: A GUIDING FRAME; A MOVABLE FRAME MOUNTED ON SAID GUIDING FRAME AND ARRANGED TO PERMIT RELATIVE MOTION BETWEEN SAID FRAMES; POST ENGAGING MEANS SECURED TO SAID MOVABLE FRAME FOR ENGAGING THE TOP OF A POST TO BE DRIVEN INTO THE GROUND; A ROTATABLE SHAFT MOUNTED ON SAID MOVABLE FRAME; FORCE TRANSMITTING MEANS SECURED TO SAID SHAFT FOR ROTATION THEREWITH; A STRIKER SLIDABLY ATTACHED TO SAID MOVABLE FRAME AND ADAPTED TO STRIKE SAID POST ENGAGING MEANS; A ROCKER ARM PIVOTALLY ATTACHED TO SAID STRIKER; A JOURNAL BLOCK SECURED TO SAID ROCKER ARM; AND A SECOND SHAFT JOURNALED IN SAID JOURNAL BLOCK AND SECURED TO SAID FORCE TRANSMITTING MEANS TO FORCE SAID STRIKER AGAINST SAID POST ENGAGING MEANS WHEN SAID FORCE TRANSMITTING MEANS IS ROTATED. 